1. Field of the Invention
The present invention relates, in general, to a device for controlling the operation of power excavators and, more particularly, to an improvement in such a device for easily controlling both the turning motion of a turret relative to a travelling part of a power excavator and the rotating motions of the working members, such as the boom, arm and bucket of the excavator, during the operation of the excavator.
2. Description of the Prior Art
As well known to those skilled in the art, power excavators are representative construction vehicles, which are preferably used for digging. A conventional crawler-type power excavator is shown in FIG. 1. As shown in FIG. 1, the crawler-type power excavator has a travelling part 1 and a turret 2. The turret 2 is mounted rotatably to the top of the travelling part 1 with a swing unit 3 interposed between the travelling part 1 and turret 2. Due to the above swing unit 3, the turret 2 can be turned in opposite directions relative to the travelling part 1. The above swing unit 3 includes a swing motor as an actuator.
The turret 2 is equipped with a control cap 4, a drive unit and various elements associated with the drive unit. The excavator also includes a plurality of working members, that is, a boom 5, arm 6 and bucket 7 which are jointed together.
The above boom 5 is jointed to the front of the turret 2, so that the boom 5 can be rotated up and down relative to the turret 2. The above arm 6 is jointed to the tip of the boom 5, so that the arm 6 can be rotated in and out relative to the boom 5. The above bucket 7 is jointed to the tip of the arm 6, so that the bucket 7 can be rotated in and out relative to the arm 6. At the joints between the working members 5, 6 and 7, a plurality of cylinder actuators 8, 9 and 10 are provided for moving the working members 5, 6 and 7.
In order to control the operation of the boom 5, arm 6, bucket 7 and swing unit 3, two control levers 11a and 11b which are shown in FIG. 2 are typically provided in the left and right sections in front of the operator's seat inside the control cap. The left control lever 11a controls the operation of both the swing unit 3 and the arm 6. That is, when the left control lever 11a is pushed leftward or rightward, the swing unit 3 along with the turret 2 is turned in either direction relative to the travelling part 1. When the left control lever 11a is pushed forward or backward, the arm 6 is rotated in or out relative to the tip of the boom 5.
Meanwhile, the right control lever 11b controls the operation of both the boom 5 and the bucket 7. That is, when the right control lever 11b is pushed leftward or rightward, the bucket 7 is rotated in or out relative to the tip of the arm 6. When the right control lever 11b is pushed forward or backward, the boom 6 is rotated up or down relative to the turret 2.
While performing the desired work such as a land finishing or loading work, the operator of the above power excavator must individually or collectively handle the control levers 11a and 11b in order to appropriately control the rotating motions of the boom 5, arm 6 and bucket 7 and control the turning motion of the turret 2 relative to the travelling part 1.
However, the above control levers 11a and 11b are inconvenient to the operator because the operator must use both hands in order to collectively handle the levers 11a and 11b. In addition, the intuitive handling directions of the levers 11a and 11b are not identified with the actual moving directions of the associated working members 5, 6 and 7 and the swing unit 3. Therefore, it is very difficult to use the control levers 11a and 11b. That means that a power excavator must be operated by a highly-skilled operator, particularly when the excavator performs delicate work, such as a land finishing or loading work.
Japanese Patent Laid-open Publication No. Hei. 2-197627 discloses "a control lever for power excavators". In the above Japanese control lever, an additional control means 71 (see the drawings, FIGS. 1 to 8, accompanied by the cited reference) is provided on the top of a typical control lever 31 (see the drawings, FIGS. 1 to 8, accompanied by the cited reference), so that the boom, arm, bucket and swing unit of a power excavator can be operated by using the control lever that has the additional control means.
However, in the above Japanese control lever, the intuitive handling directions of the lever with the additional control means are not identified with the actual moving directions of the boom, arm, bucket and swing unit. In this regard, the intuitive handling of the lever may cause a safety accident of the power excavator during the operation of the excavator. Another problem of the above Japanese control lever resides in that the operator must be highly skilled in order to perform the operation of the lever.